Method for Recovery of Propane and Heavier Hydrocarbons

Abstract

A method for recovering C 2 and higher weight hydrocarbons, or alternatively C 3 and higher weight hydrocarbons, from low pressure gas, wherein the method avoids the need to significantly compress contaminated low pressure gas in most cases, and is robust in response to pressure and temperature variations in the low pressure gas feed.

1 . A method for processing an low pressure gas inlet stream to recover C 3  and higher weight hydrocarbons, comprising the steps of
 dehydrating said low pressure gas inlet stream,   cooling said low pressure gas inlet stream to form a partially condensed hydrocarbon feed,   separating a first liquid stream and a first vapor stream from said partially condensed hydrocarbon feed,   compressing said first vapor stream,   feeding said compressed first vapor stream to an absorber bottom,   feeding said first liquid stream to a distillation column,   separating top product from said distillation column into a second vapor stream and a second liquid stream,   returning said second liquid stream to said distillation column,   feeding said second vapor stream to the top of said absorber,   feeding absorber bottom product to said distillation column, and   recovering C 3  and higher weight hydrocarbons as bottom product from said distillation column.   
     
     
         2 . The method of  claim 1 , additionally comprising the step of pre-chilling said low pressure gas inlet stream prior to the step of dehydrating said low pressure gas inlet stream. 
     
     
         3 . The method of  claim 1 , additionally comprising the steps of
 recovering top vapor from said absorber, and   cooling said top vapor to provide a lean gas output.   
     
     
         4 . The method of  claim 1 , additionally comprising the step of providing a closed loop refrigeration system to provide refrigeration for the process. 
     
     
         5 . The method of  claim 1 , additionally comprising the step of providing a closed loop turbo expander refrigeration system to provide refrigeration for the process. 
     
     
         6 . The method of  claim 1 , wherein the step of cooling said low pressure gas inlet stream to form a partially condensed hydrocarbon feed comprises the step of cooling said low pressure gas inlet stream to about −40 to −85° F. 
     
     
         7 . The method of  claim 1 , wherein the step of compressing said first vapor stream comprises the step of compressing said first vapor stream to about 120 to 240 psia. 
     
     
         8 . The method of  claim 1 , additionally comprising the step of warming said first vapor stream to about 20 to 85° F. prior to the step of compressing said first vapor stream. 
     
     
         9 . The method of  claim 1 , additionally comprising the step of cooling said first compressed vapor stream to about −50 to −104° F. 
     
     
         10 . The method of  claim 1 , additionally comprising the step of operating said absorber at about 100 to 230 psia. 
     
     
         11 . The method of  claim 1 , additionally comprising the step of operating said distillation column at about 120 to 320 psia at the bottom. 
     
     
         12 . The method of  claim 1 , additionally comprising the step of operating said distillation column at about 110 to 310 psia at the top. 
     
     
         13 . The method of  claim 1 , additionally comprising the step of maintaining said distillation column bottom temperature at about 85 to 160° F. 
     
     
         14 . The method of  claim 1 , additionally comprising the step of flashing part of said bottom product for use as a refrigerant.